Examples of unusual ionospheric observations by the CSES prior to earthquakes

Abstract

The CSES (China seismic electromagnetic satellite) was launched on February 2, 2018 in a circular polar orbit at an altitude of ~507 km. One of the main objectives of CSES is to search for and characterize ionospheric perturbations that can be associated with seismic activities, to better understand the generation mechanism of such perturbations. Its scientific payload can measure a broad frequency range of electromagnetic waves and some important plasma parameters. This paper is a first‐hand study of unusual observations recorded by the CSES over seismic regions prior to four earthquakes with M >7.0 since the satellite's launch. CSES detectors measured irregularities near the epicenter of these four earthquakes. It is already clear that data from instruments onboard the CSES will be of significant help in studies of characteristics of ionospheric perturbations related to earthquakes and their generation mechanisms.

Introduction to special section on the China Seismo-Electromagnetic Satellite and initial results

“…The spatial distribution of N e / T e from these two satellite observations is essentially identical, which verifies that the LAP instrument onboard the CSES is working well. Furthermore, Yan R et al () have conducted typical case studies for an earthquake and a magnetic storm event. They report that there are obvious changes before and after an earthquake or a magnetic storm, indicating that ionospheric parameters can be affected by an earthquake or a magnetic storm.…”

“…Yan R et al () have analyzed unusual ionospheric signatures obtained from CSES prior to four different earthquakes—one with shallow depth (0–70 km), one with moderate depth (70–300 km) and two with deep focus (>300 km).…”

“…Since its launch in February, the CSES has detected several strong earthquakes with M s ≥ 7.0. Yan R et al (2018b) have analyzed unusual ionospheric signatures obtained from CSES prior to four different earthquakes-one with shallow depth (0-70 km), one with moderate depth (70-300 km) and two with deep focus (>300 km). An Ms 7.1 earthquake took place at Ile Hunter, Caledonia (21.95°S, 170.1°E), on August 29, 2018, at a depth of 20 km.…”

Comparison of Electron Density and Temperature From the CSES Satellite With Other Space‐Borne and Ground‐Based Observations

“…Among them, the Langmuir probe (LAP) measures Ne and Te within the range of 5 × 10 8 –1 × 10 13 m −3 and 500–10,000 K, respectively. The preliminary application of the CSES Ne and Te has been presented, for example, Yan, Guan et al (2018) and Yan, Shen et al (2018). The primary aim of this paper is to evaluate the reliability of CSES LAP measurements.…”

Seismic-ionospheric perturbations in ionospheric TEC and plasma parameters associated with the 14 July 2019 Mw7.2 Laiwui earthquake detected by the GPS and CSES

“…The CSES is the first space-based platform in China for both earthquake observation and geophysical field measurement, and it is a sun-synchronous satellite orbiting at a height of approximately 507 km with a descending node of 14:00 local time, an ascending node time of 02:00 LT with an inclination of 97.4°. The distance between its neighboring tracks is 2650 km (24° in longitude) in one day, while reduced to 530 km (4° in longitude) in a revisit period of 5 days(Yan et al 2018). The main objectives of this mission are to monitor the near-Earth space environment and investigate possible electromagnetic perturbations related to natural disasters and human activities (Shen et al 2018).…”